<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <child1></child1>
   
  </div>
  <div id="app1">
  <child1></child1>
   

  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  <script>
    Vue.component ('child1' , {
      template:'<h1>组件1</h1>'
    })
    const app = new Vue({
      el:'#app',
      components:{
        child2:{
          template:'<h1>组件2</h1>'
        }
      }
    })
    const app1 = new Vue({
      el:'#app1',
      components:{
        child3:{
          template:'<h1>组件3</h1>'
        }
      }
    })
  </script>
</body>
</html>